Firstly was that to the centre of the towball and I presume that this was a PT02 vehicle. The EC Directive 94/20/EC states that the tow ball height (to the centre of the ball) should be between 350 and 420mm from the ground with the vehicle in a 'laden' state.
On my Discovery 4 which has a demountable LR towball fitted. The towball height is 420mm. The vehicle has air suspension so there is no difference in height between laden and unladen state whilst the engine is running.
At this height, coupled, my horse trailer loaded could do with an extra 50 -100 mm so say 500 mm acceptable
My 3.5 T trailer is a pain in the butt, I have to jump on the drawbar to lower it to connect it (yes I could just raise the air suspension to connect) but it runs nose low and when empty the back tandem vehicles can on some gradients be off the ground. So an extra 100mm wouldn't go amiss. Again 520 mm acceptable.
The IG has coil springs so when "with the vehicle in a 'laden' state." with a trailer attached it is conceivable that the towball drops to the 420mm height. Thus complying with EC Directive 94/20/EC. As laden state isn't defined that bit is rather subjective.
I am not worried about single axle trailers, they are only 0.75T.
I think IA know what they are doing and are happy to wait till I get my hands on one.
